(1) Field of the Invention
This invention relates to a power supply terminal for supplying power to a back wiring board (BWB) and a back board for supplying power and, more particularly, to a power supply terminal with a noise filter circuit and a back board with a noise filter circuit.
(2) Description of the Related Art
With the progress and development of various communication systems, such as cellular telephones and the Internet, in various forms, the amount of information they process is increasing steadily in various forms. In the circumstances, there is a tendency to demand of various communication systems higher information density, larger transmission capacity of information, and higher-level functions. To satisfy these demands, consumption of power by each of communication units included in various communication systems has increased and it has been required to have a structure which can withstand a powerful electric current. And furthermore, to process high-density and high-frequency signals, the structure of a BWB included in each communication unit is getting more multilayered steadily and its thickness also tends to increase.
Usually power supply terminals are connected to BWBs included in these communication units by the use of press fit terminals without soldering.
FIG. 10 is a perspective view showing a conventional structure in which power supply is connected to a BWB 151 by the use of a power supply terminal 100 with press fit terminals 121. FIG. 11 is a sectional view taken along the line Dxe2x80x94D of FIG. 10.
The power supply terminal 100 includes pressure connection terminals 123 for supplying power, press fit terminals 121 inserted into the BWB 151, and a terminal body 120 where part of each press fit terminal 121 is housed. The pressure connection terminals 123 are electrically connected to the press fit terminals 121 by pressure connection terminal fixing screws 124.
The power supply terminal 100 is inserted into the BWB 151 from one side of the BWB 151. Capacitors 111 included in a noise filter circuit are mounted on the other side of the BWB 151.
A back panel 152 is located on the pressure connection terminal 123 side of the terminal body 120 and the sides of the terminal body 120 and portions around them are covered with a shield 140. The shield 140 is fixed onto the BWB 151 with screws 131a and 131b and are fixed onto the back panel 152 with screws 131c and 131d. 
Under the conventional method, however, capacitors included in a noise filter circuit are mounted directly on a BWB. Moreover, this BWB may warp. In such a case, a capacitor included in this noise filter circuit will be damaged when press fit terminals are inserted into or pulled out of the BWB, when packages are inserted into or pulled out of connectors mounted on the BWB, or when the BWB is fitted on an enclosure for a unit.
Furthermore, parts, such as connectors, which cannot withstand reflow soldering are mounted on a BWB. Efficiency in work performed to mount parts on a BWB must also be considered. As a result, capacitors included in a noise filter circuit will be mounted on a BWB by manual soldering with a soldering iron. Therefore, a capacitor included in this noise filter circuit may also be damaged by thermal stresses at this soldering time.
Moreover, if high-frequency capacitors are used in a noise filter circuit, these high-frequency capacitors in the noise filter circuit must be mounted nearby press fit terminals to fully show their noise filter characteristics. However, mounting high-frequency capacitors nearby press fit terminals by manual soldering involves very difficult work. Practically, this means that high-frequency capacitors cannot be used in a noise filter circuit.
In addition, with conventional power supply terminals press fit terminals are inserted into a BWB from one side of the BWB and capacitors included in a noise filter circuit are mounted on the other side of the BWB. Therefore, a shield cannot be fixed with a screw at a position on a BWB where a noise filter circuit is formed. As a result, a shield cannot be located near press fit terminals.
The present invention was made under the background circumstances as described above. An object of the present invention is to provide a power supply terminal which can prevent damage to a capacitor included in a noise filter circuit due to a BWB""s warp or thermal stresses at soldering time.
Another object of the present invention is to provide a power supply terminal which makes it possible to use high-frequency capacitors in a noise filter circuit.
Still another object of the present invention is to provide a power supply terminal which makes it possible to locate a shield near press fit terminals.
In order to achieve the above objects, a power supply terminal for supplying power to a back wiring board is provided. This power supply terminal comprises a terminal body as a base, press fit terminals at least part of each of which is housed in the terminal body and which are electrically connected to the back wiring board by being inserted into the back wiring board, and a noise filter circuit substrate which is separate from the back wiring board and on which capacitors included in a noise filter circuit electrically connected to the press fit terminals are mounted.
Furthermore, according to the present invention, a back board for supplying power is provided. This back board comprises a back wiring board on which a pattern for supplying power is formed, a power supply terminal including a terminal body as a base and press fit terminals at least part of each of which is housed in the terminal body and which are electrically connected to the back wiring board by being inserted into the back wiring board, and a noise filter circuit substrate which is separate from the back wiring board and on which capacitors included in a noise filter circuit electrically connected to the press fit terminals are mounted.
The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.